router interface up connected to switch interface down - but router status = up.

[SJ K]

Hi all,

My router R2 fa0/0 and fa0/1 are connected to 2 L3 switches on their fa0/2 ports respectively.
I have shutdown all interfaces on the L3 switches. but on my router, i still see

R2#show ip int bri
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            192.168.3.1     YES manual up                    down
FastEthernet0/1            192.168.4.1     YES manual up                    down

======================================================================

I would have thought if i have shutdown the switches interfaces, the respective interfaces on the Router would be down too.

Is it not the case ?

Regards,
Noob

[Liam Kenneally]

Hi KOH SZE JIE, 

This is normal behavior; If you have an interface UP; the line protocol may go up and down. But the Status (of the interface) will not change unless you make a configuration change. 

Please see below a breakdown of your "show ip int brief" 

Method

is set to 'Manual' This means you manually configured the interface from the CLI.

Status

is 'UP' This means the interface is up. Basically this means you did a "no shutdown" on the port. 

There are three modes here 

Down - The interface is shutdown (Default on most routers) 

Administratively down - You have gone under the interface and issued a "shutdown" 

UP - You have issued a "No shutdown" on the interface. 

Protocol 

Down - This means a routing protocol is not active on the interface. This makes sense as you have shutdown the remote end(in your case your L3 switch.

I hope this helps.

Kind Regards,

Liam

*** EDIT *** 

After a bit of digging, I found the following Cisco document; this explains the entire show command more concisely then I could :)  

http://www.cisco.com/c/en/us/td/docs/optical/cpt/r9_3/command/reference/cpt93_cr/cpt93_cr_chapter_01110.html 

[SJ K]

Hi Liam,

Thanks and sorry for the late reply.

q1) Can I check under what circumstances will a interface status show as "Down"  and not "Administratively down" ?

q2) If i issue a no shut and the interface is up, but then i pull out the physical cable, will the status still show as Up ?

Regards,
Noob